Perioperative medicine is a shared enterprise among surgeons, anesthesiologists, and internists. Internists contribute unique longitudinal knowledge of comorbidities, functional status, and medication management, and are essential to three domains: risk stratification using guideline-based, stepwise frameworks (e.g., surgical/procedural urgency, active cardiac conditions, procedure risk, functional capacity, calculators, and selective biomarkers); medical optimization across cardiovascular, pulmonary, renal, hepatic, endocrine, hematologic, infectious, and nutritional issues; and effective communication that is concise, actionable, and within scope. The internist’s role is not to prescribe anesthetic technique or intraoperative targets but to quantify risk, distinguish modifiable from non-modifiable factors, document optimization steps (and remaining gaps), and provide clear medication plans (e.g., beta-blocker continuation, individualized angiotensin converting enzyme inhibitor (ACEi)/angiotensin receptor blocker (ARB) approach, anticoagulant/antiplatelet coordination, including neuraxial implications, and stress-dose steroids when indicated). Internists also anticipate noncardiac risks such as pulmonary complications, delirium, acute kidney injury, and decompensation of chronic disease, which can aid and promote prehabilitation, infection control, and transitions of care. High-risk populations (e.g., severe valvular disease, heart failure, pulmonary arterial hypertension (PAH), advanced chronic kidney disease/cirrhosis, frailty) warrant multidisciplinary planning and, when appropriate, reconsideration of timing or setting. By aligning recommendations with patient values through shared decision-making, internists help determine surgical appropriateness and expectations. Ultimately, the internist’s role strengthens safety and outcomes by integrating evidence-based assessment with collaborative, scope-appropriate guidance that supports anesthesiology’s intraoperative expertise and the surgeon’s procedural goals.